---
kind: "range"
citation: "14 C.F.R. §§ 29.1041–29.1049"
title: "14"
from: "29.1041"
to: "29.1049"
count: 5
url: "https://uscodex.org/cfr/14/29.1041..29.1049"
---

# §29.1041. General.

- (a) The powerplant and auxiliary power unit cooling provisions must be able to maintain the temperatures of powerplant components, engine fluids, and auxiliary power unit components and fluids within the temperature limits established for these components and fluids, under ground, water, and flight operating conditions for which certification is requested, and after normal engine or auxiliary power unit shutdown, or both.
- (b) There must be cooling provisions to maintain the fluid temperatures in any power transmission within safe values under any critical surface (ground or water) and flight operating conditions.
- (c) Except for ground-use-only auxiliary power units, compliance with paragraphs [(a)](#a) and [(b)](#b) of this section must be shown by flight tests in which the temperatures of selected powerplant component and auxiliary power unit component, engine, and transmission fluids are obtained under the conditions prescribed in those paragraphs.

# §29.1043. Cooling tests.

- (a) **General.** For the tests prescribed in [§ 29.1041(c)](/cfr/14/29.1041.md?p=c), the following apply:
  - (1) If the tests are conducted under conditions deviating from the maximum ambient atmospheric temperature specified in [paragraph (b)](#b) of this section, the recorded powerplant temperatures must be corrected under paragraphs [(c)](#c) and [(d)](#d) of this section, unless a more rational correction method is applicable.
  - (2) No corrected temperature determined under [paragraph (a)(1)](#a-1) of this section may exceed established limits.
  - (3) The fuel used during the cooling tests must be of the minimum grade approved for the engines, and the mixture settings must be those used in normal operation.
  - (4) The test procedures must be as prescribed in [§§ 29.1045 through 29.1049](/cfr/14/29.1045..29.1049.md).
  - (5) For the purposes of the cooling tests, a temperature is “stabilized” when its rate of change is less than 2 °F per minute.
- (b) **Maximum ambient atmospheric temperature.** A maximum ambient atmospheric temperature corresponding to sea level conditions of at least 100 degrees F. must be established. The assumed temperature lapse rate is 3.6 degrees F. per thousand feet of altitude above sea level until a temperature of −69.7 degrees F. is reached, above which altitude the temperature is considered constant at −69.7 degrees F. However, for winterization installations, the applicant may select a maximum ambient atmospheric temperature corresponding to sea level conditions of less than 100 degrees F.
- (c) **Correction factor (except cylinder barrels).** Unless a more rational correction applies, temperatures of engine fluids and powerplant components (except cylinder barrels) for which temperature limits are established, must be corrected by adding to them the difference between the maximum ambient atmospheric temperature and the temperature of the ambient air at the time of the first occurrence of the maximum component or fluid temperature recorded during the cooling test.
- (d) **Correction factor for cylinder barrel temperatures.** Cylinder barrel temperatures must be corrected by adding to them 0.7 times the difference between the maximum ambient atmospheric temperature and the temperature of the ambient air at the time of the first occurrence of the maximum cylinder barrel temperature recorded during the cooling test.

# §29.1045. Climb cooling test procedures.

- (a) Climb cooling tests must be conducted under this section for—
  - (1) Category A rotorcraft; and
  - (2) Multiengine category B rotorcraft for which certification is requested under the category A powerplant installation requirements, and under the requirements of [§ 29.861(a)](/cfr/14/29.861.md?p=a) at the steady rate of climb or descent established under [§ 29.67(b)](/cfr/14/29.67.md?p=b).
- (b) The climb or descent cooling tests must be conducted with the engine inoperative that produces the most adverse cooling conditions for the remaining engines and powerplant components.
- (c) **Each operating engine must—**
  - (1) For helicopters for which the use of 30-minute OEI power is requested, be at 30-minute OEI power for 30 minutes, and then at maximum continuous power (or at full throttle when above the critical altitude);
  - (2) For helicopters for which the use of continuous OEI power is requested, be at continuous OEI power (or at full throttle when above the critical altitude); and
  - (3) For other rotorcraft, be at maximum continuous power (or at full throttle when above the critical altitude).
- (d) After temperatures have stabilized in flight, the climb must be—
  - (1) **Begun from an altitude not greater than the lower of—**
    - (i) 1,000 feet below the engine critcal altitude; and
    - (ii) 1,000 feet below the maximum altitude at which the rate of climb is 150 f.p.m; and
  - (2) Continued for at least five minutes after the occurrence of the highest temperature recorded, or until the rotorcraft reaches the maximum altitude for which certification is requested.
- (e) For category B rotorcraft without a positive rate of climb, the descent must begin at the all-engine-critical altitude and end at the higher of—
  - (1) The maximum altitude at which level flight can be maintained with one engine operative; and
  - (2) **Sea level.**
- (f) The climb or descent must be conducted at an airspeed representing a normal operational practice for the configuration being tested. However, if the cooling provisions are sensitive to rotorcraft speed, the most critical airspeed must be used, but need not exceed the speeds established under [§ 29.67(a)(2)](/cfr/14/29.67.md?p=a-2) or [§ 29.67(b)](/cfr/14/29.67.md?p=b). The climb cooling test may be conducted in conjunction with the takeoff cooling test of [§ 29.1047](/cfr/14/29.1047.md).

# §29.1047. Takeoff cooling test procedures.

- (a) **Category A.** For each category A rotorcraft, cooling must be shown during takeoff and subsequent climb as follows:
  - (1) Each temperature must be stabilized while hovering in ground effect with—
    - (i) The power necessary for hovering;
    - (ii) The appropriate cowl flap and shutter settings; and
    - (iii) **The maximum weight.**
  - (2) After the temperatures have stabilized, a climb must be started at the lowest practicable altitude and must be conducted with one engine inoperative.
  - (3) The operating engines must be at the greatest power for which approval is sought (or at full throttle when above the critical altitude) for the same period as this power is used in determining the takeoff climbout path under [§ 29.59](/cfr/14/29.59.md).
  - (4) At the end of the time interval prescribed in [paragraph (b)(3)](#b-3) of this section, the power must be changed to that used in meeting [§ 29.67(a)(2)](/cfr/14/29.67.md?p=a-2) and the climb must be continued for—
    - (i) Thirty minutes, if 30-minute OEI power is used; or
    - (ii) At least 5 minutes after the occurrence of the highest temperature recorded, if continuous OEI power or maximum continuous power is used.
  - (5) The speeds must be those used in determining the takeoff flight path under [§ 29.59](/cfr/14/29.59.md).
- (b) **Category B.** For each category B rotorcraft, cooling must be shown during takeoff and subsequent climb as follows:
  - (1) Each temperature must be stabilized while hovering in ground effect with—
    - (i) The power necessary for hovering;
    - (ii) The appropriate cowl flap and shutter settings; and
    - (iii) **The maximum weight.**
  - (2) After the temperatures have stabilized, a climb must be started at the lowest practicable altitude with takeoff power.
  - (3) Takeoff power must be used for the same time interval as takeoff power is used in determining the takeoff flight path under [§ 29.63](/cfr/14/29.63.md).
  - (4) At the end of the time interval prescribed in [paragraph (a)(3)](#a-3) of this section, the power must be reduced to maximum continuous power and the climb must be continued for at least five minutes after the occurance of the highest temperature recorded.
  - (5) The cooling test must be conducted at an airspeed corresponding to normal operating practice for the configuration being tested. However, if the cooling provisions are sensitive to rotorcraft speed, the most critical airspeed must be used, but need not exceed the speed for best rate of climb with maximum continuous power.

# §29.1049. Hovering cooling test procedures.


The hovering cooling provisions must be shown—

- (a) At maximum weight or at the greatest weight at which the rotorcraft can hover (if less), at sea level, with the power required to hover but not more than maximum continuous power, in the ground effect in still air, until at least five minutes after the occurrence of the highest temperature recorded; and
- (b) With maximum continuous power, maximum weight, and at the altitude resulting in zero rate of climb for this configuration, until at least five minutes after the occurrence of the highest temperature recorded.